Recently, in order to improve link quality between a transmission end and a reception end and support high data transmission rate according to requirements of a next generation wireless access system, schemes utilizing multiple antennas are actively studying. Such schemes as SFBC (space frequency block coding), SM (spatial multiplexing), CL-MIMO (closed-loop MIMO/beamforming), ZFBF (zero-forcing beamforming) and the like are applied to LTE or LTE-A commercial system.
In general, due to a reason such as a physical space, power supply and the like, it is considered that more antennas are installed in an eNode B rather than a user equipment in a mobile communication system. According to a current LTE-A system (release-10), maximum 8 Tx systems are supported. Among the schemes improving the link quality using multiple antennas, if channel state information is usable by a transmission end, a beamforming scheme can provide best performance. According to the beamforming scheme, as the number of transmission antennas increases, a gain of transmit power saving or improved link quality can be obtained more. And, as the number of antennas increases, a sharp beam can be formed and may have more orthogonal beams at the same time. In particular, there may exist more reception ends capable of receiving data of each of the reception ends at the same time. To this end, a system, i.e., a massive MIMO system, capable of supporting a large-scale antenna more than legacy 8 Tx is considering.